How to Upgrade

If you are running an older version, shut it down. Wait until it has completely
shut down (which might take a few minutes for older versions), then run the
installer (on Windows) or just copy over /Applications/Bitcoin-Qt (on Mac)
or bitcoind/bitcoin-qt (on Linux).

The first time you run version 0.15.0 or higher, your chainstate database will
be converted to a new format, which will take anywhere from a few minutes to
half an hour, depending on the speed of your machine.

The file format of fee_estimates.dat changed in version 0.15.0. Hence, a
downgrade from version 0.15 or upgrade to version 0.15 will cause all fee
estimates to be discarded.

Note that the block database format also changed in version 0.8.0 and there is no
automatic upgrade code from before version 0.8 to version 0.15.0. Upgrading
directly from 0.7.x and earlier without redownloading the blockchain is not supported.
However, as usual, old wallet versions are still supported.

Downgrading warning

The chainstate database for this release is not compatible with previous
releases, so if you run 0.15 and then decide to switch back to any
older version, you will need to run the old release with the -reindex-chainstate
option to rebuild the chainstate data structures in the old format.

If your node has pruning enabled, this will entail re-downloading and
processing the entire blockchain.

Compatibility

Bitcoin Core is extensively tested on multiple operating systems using
the Linux kernel, macOS 10.8+, and Windows Vista and later. Windows XP is not supported.

Bitcoin Core should also work on most other Unix-like systems but is not
frequently tested on them.

Notable changes

Denial-of-Service vulnerability CVE-2018-17144

A denial-of-service vulnerability exploitable by miners has been discovered in
Bitcoin Core versions 0.14.0 up to 0.16.2. It is recommended to upgrade any of
the vulnerable versions to 0.15.2 or 0.16.3 as soon as possible.